Editing Contrast effect (section)

=== Metacontrast and paracontrast ===
[[Image:Metacontrast and paracontrast.jpg|296x296px|thumb|Metacontrast and paracontrast|alt=]]Metacontrast and paracontrast involve both time and space. When one half of a circle is lit for 10 [[millisecond]]s (ms), it is at its maximal intensity. If the other half is displayed at the same time (but 20–50 ms later), there is a mutual inhibition: the left side is darkened by the right half (''metacontrast''), and the center may be completely obliterated. At the same time, there is a slight darkening of the right side due to the first stimulus (''paracontrast'').<ref>"Eye, human". Encyclopædia Britannica. 2008. [[Encyclopædia Britannica 2006 Ultimate Reference Suite DVD]].</ref>{{Clarify|date=June 2015}}